In subjects with a coagulopathy, such as in human beings with haemophilia A and B, various steps of the coagulation cascade are rendered dysfunctional due to, for example, the absence or insufficient presence of a coagulation factor. Such dysfunction of one part of the coagulation cascade results in insufficient blood coagulation and potentially life-threatening bleeding, or damage to internal organs, such as the joints. Subjects such as human beings with haemophilia A and B may receive coagulation factor replacement therapy such as exogenous Factor VIII or Factor IX, respectively. However, such patients are at risk of developing “inhibitors” (antibodies) to such exogenous factors, rendering formerly efficient therapy ineffective. Furthermore, exogenous coagulation factors may only be administered intravenously, which is of considerable inconvenience and discomfort to patients. For example, infants and toddlers may have to have intravenous catheters surgically inserted into a chest vein, in order for venous access to be guaranteed. This leaves them at great risk of developing bacterial infections and thrombotic complications. Subjects with a coagulopathy may only receive therapy after a bleed has commenced, rather than as a precautionary measure, which often impinges upon their general quality of life. Thus, there are still many unmet medical needs in the haemophilia community, in particular, and in subjects with coagulopathies, in general.
The coagulation cascade is normally set into motion upon vessel wall injury, which exposes sub-endothelial tissue factor (TF) to the components of circulating blood. In brief, TF forms a complex with Factor VII/Factor VIIa (FVII/FVIIa) on the surface of TF-expressing cells. This complex activates Factor X (FX) to Factor Xa (FXa) which, with Factor Va (FVa) as cofactor, leads to the generation of a limited amount of thrombin (FIIa). Small amounts of thrombin activate platelets, which results in surface exposure of phospholipids that support the binding of the tenase complex, Factor VIIIa/Factor IXa (FVIIIa/FIXa). The tenase complex activates large amounts of FX to FXa, which subsequently results in the generation of a large amount of thrombin. A full thrombin burst is needed for the formation of a mechanically strong fibrin structure and stabilization of the haemostatic plug.
In individuals with haemophilia, FVIII or FIX is present at low levels, or may be entirely absent. Due to the lack of tenase activity, the capacity to generate FXa is low and insufficient to support the propagation phase of coagulation. In contrast, the TF-mediated initiation phase of coagulation is not dependent on the formation of the tenase complex. Initiation of coagulation via the TF-pathway will, however, be blocked by plasma inhibitors shortly after the initial FXa generation. One such inhibitor is tissue factor pathway inhibitor (TFPI), which inhibits both FXa and TF/FVIIa and plays a key role as a feed-back inhibitor of on-going coagulation. TFPI is a strong inhibitor of the TF-FVIIa complex only in the presence of FXa. Thus, efficient inhibition of TF/FVIIa requires generation of FXa, formation of the FXa/TFPI complex, and a subsequent formation of the ternary TF/FVIIa/FXa/TFPI complex.
Several pools of TFPI exist in vivo. A major fraction is bound to the vascular endothelium, a minor fraction is associated with lipoproteins in the blood, a small fraction is present in platelets and, finally, a small amount exists as free, circulating TFPI. Furthermore, TFPI exists as TFPIalpha, TFPIbeta and TFPIgamma forms. Neutralization of the inhibitory activity of certain fractions of TFPI may prove efficient in treatment of undesired bleedings.
Antibodies that are capable of binding TFPI are known in the art. Several documents disclose antibodies that are capable of binding to the K3 domain of TFPI, namely:                J. Biochem, 1995, 118 (1): 178-182.        Blood Coagul. Fibrinolyis, 1999, 10 (6): 309-19.        JP6153981A.        
These references do not disclose TFPI antibodies for the treatment of subjects with a coagulopathy.
There is still a need in the art of medicine for pharmaceuticals which may be used to enhance coagulation. There is a need for pharmaceuticals which may be administered not only intravenously but also by other routes of administration, such as subcutaneously. Thus, there is a need for pharmaceuticals, such as antibodies, which are pro-coagulant even when administered in low doses and/or which have a high bioavailability. Furthermore, there is a need for pharmaceuticals, such as antibodies, which are suitable for the prophylactic treatment of individuals with a congenital or acquired coagulopathy such as haemophilia A, haemophilia B, haemophilia A with inhibitors or haemophilia B with inhibitors. More specifically, there is a need for pharmaceuticals, such as antibodies, that lower the threshold for FVIII or FIX activity in individuals with haemophilia A and haemophilia B, respectively. Within the particular realm of antibodies that are capable of binding TFPI, there is a need for antibodies which do not bind to all pools of TFPI, such as antibodies which do not affect the function of endothelial cell-bound TFPI, such as the GPI-anchored pool of TFPI. More specifically, there is a need for TFPI antibodies that demonstrate dose linearity with respect to their half-life in plasma.
Disclosed herein are antibodies which are suitable for use as pharmaceuticals. Such antibodies may have a substantial impact upon the quality of life of—not least—individuals with haemophilia A or B, with or without inhibitors.